My breeder has had some financial troubles (laid off from her job!!) so she hasn't been able to screen her cats recently; at least she was very upfront about it and brought up HCM without me having to ask. Unfortunately I didn't know it was such a huuuuge problem at the time. Like others have mentioned, I thought I did my research but obviously I know a lot more now than I did before. She does have one of those cats on the HCM-positive list in almost all her cats but I think this is unavoidable, as HCM is in ALL the lines. And another cat on there is the grandsire of one of her studs so she retired him, which was responsible of her. It sucks that even if you do screen every year you can't guarantee a kitten won't have it. I guess I feel better that she often breeds her cats until they are ~4ish and then keeps them as altered pets for a long time. I know Toast's mom is spayed and a pet in her home; his dad is still a stud... and she also has Toast's older brothers from different litters in her home too. I am more worried about Snowpoke because his parents are young (1-2 years old). It seems though, with the unreliability of screening, that the only way to guarantee not having HCM is by not getting a bengal at all.
Of course screening greatly minimizes the risk, but it's still very scary.